Differential pressure sensors including built-in pressure sensor chips, which include a sensor diaphragm that outputs a signal corresponding to the difference between pressures applied to one and the other surfaces of the sensor diaphragm, have been used as industrial differential pressure sensors.
Such a differential pressure sensor is structured so that measurement pressures applied to high-pressure-side and low-pressure-side pressure-receiving diaphragms are transmitted to one and the other surfaces of the sensor diaphragm by enclosed liquid that serves as a pressure transmitting medium. Strain of the sensor diaphragm is detected as, for example, a change in resistance of a strain resistance gauge, and the resistance change is converted into an electrical signal to be output.
A differential pressure/static pressure composite sensor is an example of a differential pressure sensor capable of measuring not only a differential pressure but also a static pressure. The differential pressure/static pressure composite sensor includes a differential-pressure diaphragm formed in a central region of a substrate and an annular static-pressure diaphragm that surrounds the outer periphery of the differential-pressure diaphragm (see, for example, PTL 1). The differential pressure/static pressure composite sensor is capable of detecting not only a differential pressure but also a static pressure by transmitting a measurement pressure applied to one or the other surface of the differential-pressure diaphragm to one surface of the static-pressure diaphragm along a branched path and applying a reference pressure to the other surface of the static-pressure diaphragm.